河道砂体内部薄夹层识别与剩余油挖潜

Identification of Thin Interlayer and Potential Tapping of Residual Oil in Channel Sand Bodies

油藏长期注水开发后,河道砂体内部部分高渗条带出现注入水低效甚至无效循环,剩余油富集在夹层附近,而河道砂体内薄夹层识别率仍较低,不利于剩余油挖潜。以大庆长垣油田北二区西部为例,应用小井距密闭取心井资料,开展河道砂体内部薄夹层精细描述,对夹层测井响应特征进行分类评价,明确其对剩余油分布的控制作用。研究结果表明,研究区夹层分为岩性夹层和物性夹层,以泥岩和粉砂岩为主,纵向上主要分布于沉积旋回顶部,平面上主要位于沉积相相变区,而剩余油集中分布于夹层附近。以薄夹层识别成果为依据,针对不同河道砂体内剩余油分布特征,采用不同方法实现厚砂体层内调整挖潜,增油降水效果明显,可供同类区块的二次开发借鉴。

Inefficient or invalid circulation of the injected water occur in partial high-permeable zones within channel sand bodies after long-term waterflood development in reservoirs,and remaining oil accumulates near interlayers.It is still difficult to identify thin interlayer in channel sand bodies,which goes against the remaining oil potential tapping.Taking the western area of District Beier of Daqing placanti-cline oilfield as an example and using the data obtained from sealed coring wells with small well spacings,the paper carries out fine de-scription of thin interlayer within channel sand bodies,classifies and evaluates the logging response characteristics of the interlayer and de-termines its controls on residual oil distribution.The study results show that the interlayers in the study area can be divided into lithological interlayer and physical-property interlayer,both of which are dominated by mudstone and siltstone,mainly distributed at the top of the sedi-mentary cycle vertically and mainly located in the sedimentary facies transformation zones in the plane.The remaining oil concentrates in the vicinity of the interlayers.Based on the identification results of the thin interlayers and according to the characteristics of the residual oil distributed in different channel sand bodies,different methods are adopted to realize the adjustment of potential tapping in thick sand layers,and the effects of increasing oil production and decreasing water production are significant,which can be the references for the sec-ondary development in similar blocks.